Purpose: Occupational exposure of firefighters involves a complex range of potential health threats from toxic chemicals, shift work, extreme heat, physical and emotional strain. The aim of this study is to examine overall and disease-specific mortality among Danish firefighters. Methods: Through systematic collection of personnel and membership records from employers and trade unions, past and present male Danish firefighters were identified (n = 11,775). Using the unique Danish personal identification number, information on additional employment, vital status and cause of death was linked to each member of the cohort from the Supplementary Pension Fund Register, the Danish Civil Registration System and the Danish Register of Causes of Death. Standardized mortality ratios (SMRs) were calculated for specific causes of death using rates for two reference groups, a random sample of the male working population (n = 262,168) and the military (n = 396,739), respectively. Results: Overall mortality was significantly reduced among the firefighters compared to both the sample of the working population and the military (SMR 0.74, 95% CI 0.69–0.78 and SMR 0.88, 95% CI 0.83–0.93). Further, the SMRs for endocrine diseases, mental disorders, non-traffic related accidents and other external causes were significantly lower against both reference groups. Death from stomach cancer was significantly increased among the full time firefighters, while part time/volunteer workers shared a significant increase in prostate cancer death compared to both references. Conclusions: Despite potential exposure to several occupational hazards, male Danish firefighters have a lower mortality than both the Danish working population in general and Danish military employees.